Architectural precast concrete wall panels are used in construction of buildings and other structures. The term “architectural precast concrete wall panels” and variants thereof as used herein refers to concrete panels that are used in forming walls that have a perimeter area of at least twenty square feet. The term “perimeter area” and variants thereof as used herein refers to the area circumscribed by an outer perimeter of the surface panel. Thus, the perimeter area is determined without consideration of any apertures through the surface.
Architectural precast concrete wall panels are typically fabricated in a factory or another location that is remote from a construction (building) site where the wall panels will be used. The wall panels are then transported to the construction site (e.g., on a truck bed). At the construction (building) site, the wall panels are erected and secured to one another to form walls of a building.
Precast concrete wall panels are formed by pouring concrete slurry into a mold that has the desired shape of the wall panel. Concrete slurry is a mixture of cement paste and aggregate material. The cement paste is usually formed from water and Portland cement powder. The aggregate material comprises granular material such as sand, gravel, or crushed stone. In the concrete slurry, the cement paste coats the granules of the aggregates and fills voids between the granules. Once mixed, the concrete slurry begins to harden.
Although alternatives are possible, the wall panels have a generally rectangular shape with a width of at least 4 feet (or 1 meter), often in the range of 4-15 fifteen feet (or 1-5 meters) inclusive, and a length of at least 10 feet (or 3 meters), often in the range of 10-50 feet (or 3-16 meters) inclusive. The wall panels are not limited to rectangular shapes though and can include various cutouts for aesthetic/design purposes (e.g., arches or points for a roof line) or for functional purpose (e.g., openings for doors, windows, etc.). Typically, the wall panels have a thickness of at least 3 inches (or 7 centimeters), often in a range of 3-9 inches (or 7-23 centimeters) inclusive, and sometimes even thicker.
Various materials can be added to the concrete. For example, steel rods, cables, or meshes can be added to reinforce the concrete. Insulating materials can also be added. In some cases, the wall panel is formed from multiple layers of concrete separated by a layer of foam insulation. The concrete panel can comprise prestressed concrete if desired.
The wall panels can be formed to have various surface textures, which may be desired for aesthetic or functional purposes. Textures can be produced by spraying an acid wash on the wall panel. The acid wash will abrade the surface of the wall panel, leaving behind a texture. Unfortunately, managing the chemicals used in the acid wash can be time consuming and expensive. Textures can also be produced using dry sand blasting equipment. However, typical dry sand blasting approaches can fill the air with dry particulate matter, which then be managed.
The present application relates to methods, techniques, and equipment for providing a surface portion of an architectural precast concrete wall panel with an abraded texture that overcome the shortcomings of such past approaches as using an acid wash or sand blasting for the abrading.